In prior art telecommunication switching systems, it is well known to synchronize a central timing unit within the telecommunication switching system to an external link. Indeed, this is commonly done so as to maintain consistent timing throughout a public telecommunication network. In prior art telecommunication systems, this was accomplished by hardwiring timing links from one or more selected external links to the central timing unit. The central timing unit then could select one of the hardwired links to synchronize the internal timing of the central timing unit.
Whereas the prior art telecommunication switching systems did provide a solution, this solution has many problems. The first problem is that the external links to which synchronization was to be performed had to be selected and then, manually hardwired links had to be installed. Because of the cost and complexity of establishing hardwired links, normally only a small set of external links such as two were selected. In addition, the hardwired links had to be duplicated for reliability purposes but if the two duplicated hardwired links should fail, then the central timing unit could not synchronize to that particular external link. In addition, new international standards require that a telecommunication switching system be able to determine which external link is connected to the best timing source and utilize that external link. This means that a prior art telecommunication switching system would have to have hardwired links to each of the external links.